Generator

ABSTRACT

A generator, such as for a gas turbine engine, includes an integrated auto transformer unit having secondary windings connected to a main windings.

BACKGROUND OF THE INVENTION

Turbine engines, and particularly gas turbine engines, also known ascombustion turbine engines, are rotary engines that extract energy froma flow of combusted gases passing through the engine onto a multitude ofturbine blades. Gas turbine engines have been used for land and nauticallocomotion and power generation, but are most commonly used foraeronautical applications such as for airplanes, including helicopters.In airplanes, gas turbine engines are used for propulsion of theaircraft.

Gas turbine engines can have two or more spools, including a lowpressure (LP) spool that provides a significant fraction of the overallpropulsion system thrust, and a high pressure (HP) spool that drives oneor more compressors and produces additional thrust by directing exhaustproducts in an aft direction. A triple spool gas turbine engine includesa third, intermediate pressure (IP) spool.

Gas turbine engines also usually power a number of different accessoriessuch as generators, starter/generators, permanent magnet alternators(PMA), fuel pumps, and hydraulic pumps, e.g., equipment for functionsneeded on an aircraft other than propulsion. For example, contemporaryaircraft need electrical power for avionics, motors, and otherelectrical equipment. A generator coupled with a gas turbine engine willconvert the mechanical power of the engine into electrical energy neededto power accessories.

Autotransformers (ATUs) are frequently used in power applications tointerconnect systems operating at different voltage classes and toreduce the harmonic contents of the generators and the ripples at theoutputs of the rectifiers. In aircrafts, autotransformers typically areused to step up or down voltages between generators and rectifiers. ATUsare separate from the generator, and add to the weight and volume of theengine. Furthermore, ATUs often require a forced liquid cooling system,which adds additional weight and volume to the engine.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a generator includes a stator having three mainwindings, at least two secondary windings connected to each of the threemain windings to form an integrated auto transformer unit, a first setof conductors connected to the three main windings, and a second set ofconductors connected to each of the at least two secondary windings.

In another embodiment, a gas turbine engine has a generator including astator having three main windings, at least two secondary windingsconnected to each of the three main windings to form an integrated autotransformer unit, a first set of conductors connected to the three mainwindings, and a second set of conductors connected to each of the atleast two secondary windings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional diagram of a gas turbine enginefor an aircraft;

FIG. 2 is a schematic block diagram of an electrical power systemarchitecture for the gas turbine engine of FIG. 1, the systemarchitecture having a generator with an integrated autotransformer unitin accordance with a first embodiment of the invention;

FIG. 3 is an electrical diagram of the generator with the integratedautotransformer unit and an AC-to-DC power converter of the electricalpower system architecture of FIG. 2.

FIG. 4 is an electrical diagram of a stator winding for the generatorwith the integrated autotransformer unit from FIG. 3;

FIG. 5 is a winding vector diagram for the stator winding from FIG. 4;

FIG. 6 is a schematic block diagram of an electrical power systemarchitecture for the gas turbine engine of FIG. 1, the systemarchitecture having an integrated autotransformer unit in accordancewith a second embodiment of the invention;

FIG. 7 is an electrical diagram of the generator with the integratedautotransformer unit and an AC-to-DC power converter of the electricalpower system architecture of FIG. 6.

FIG. 8 is an electrical diagram of a stator winding for the generatorwith the integrated autotransformer unit from FIG. 3;

FIG. 9 is a winding vector diagram for the stator winding from FIG. 8;

FIG. 10 is a schematic block diagram of an electrical power systemarchitecture for the gas turbine engine of FIG. 1, the systemarchitecture having a generator with an integrated autotransformer unitin accordance with a third embodiment of the invention;

FIG. 11 is an electrical diagram of the generator with the integratedautotransformer unit and an AC-to-DC power converter of the electricalpower system architecture of FIG. 10.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The described embodiments of the present invention are generallydirected to generators for converting mechanical power to electricalpower. Embodiments of the invention are described with respect to powergeneration from an aircraft engine, and more particularly to anelectrical power system architecture having at least one generator whichenables production of electrical power from a turbine engine, preferablya gas turbine engine. It will be understood, however, that the inventionis not so limited and has general application to electrical power systemarchitectures in non-aircraft applications, such as other mobileapplications and non-mobile industrial, commercial, and residentialapplications.

FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine 10for an aircraft. Engine 10 includes, in downstream serial flowrelationship, a fan section 12 including a fan 14, a booster or lowpressure (LP) compressor 16, a high pressure (HP) compressor 18, acombustion section 20, a HP turbine 22, and a LP turbine 24. A HP shaftor spool 26 drivingly connects HP turbine 22 to HP compressor 18 and aLP shaft or spool 28 drivingly connects LP turbine 24 to LP compressor16 and fan 14. HP turbine 22 includes an HP turbine rotor 30 havingturbine blades 32 mounted at a periphery of rotor 30. Blades 32 extendradially outwardly from blade platforms 34 to radially outer blade tips36.

FIG. 2 is a schematic block diagram of an electrical power systemarchitecture 40 according to a first embodiment of the invention. Thesystem architecture 40 includes multiple engine systems, shown herein asincluding at least a left engine system 42 and a right engine system 44.The left and right engine systems 42, 44 may be substantially identical;therefore, only the left engine system 42 will be described in detailfor the sake of brevity. The left engine system 42 can include the HPand LP spools 26, 28 of the gas turbine engine 10 shown in FIG. 1,although the system architecture 40 has application to other engines aswell. The left engine system 42 shown herein uses mechanical powerprovided by two spools, the HP spool 26 and the LP spool 28. However,the system architecture 40 could also be implemented on an engine havingmore than two spools, such as a 3-spool engine having an intermediatepressure spool in addition to the HP and LP spools. The systemarchitecture 40 can further include an auxiliary power unit (APU) 46 ofthe aircraft and an external power source (EPS) 48. As shown herein, theAPU 46 and EPS 48 each have a DC output 50, 52, respectively.

In the embodiment illustrated, the left engine system 42 includes afirst autotransformer unit (ATU) integrated generator 56, shown hereinas an ATU integrated starter-generator 56, configured to producevariable frequency (VF) AC power from mechanical power supplied by theHP spool 26, and a second ATU integrated generator 58 configured toproduce constant frequency (CF) AC power from mechanical power suppliedby the LP spool 28.

The ATU integrated starter-generator 56 includes a power generationsection 60 and an ATU section 62. As will be explained in greater detailbelow, the ATU section 62 is integrated with the power generationsection 60 by integrating some of the electrical windings necessary forpower transformation on the electrical winding of the power generationsection 60. This essentially eliminates winding duplication in the powergeneration section 60 and the ATU section 62, which can translate intoweight and cost savings for the aircraft.

The HP spool 26 can be operably coupled with the ATU integratedstarter-generator 56 by an HP drive assembly having an inputmechanically coupled to the HP spool 26 and an output mechanicallycoupled to the power generation section 62. One embodiment of the HPdrive assembly is an accessory gearbox 64, where the ATU integratedstarter-generator 56 can be mounted and coupled to the accessory gearbox64. Within the accessory gearbox 64, power may also be transferred toother engine accessories. The power generation section 60 of the ATUintegrated starter-generator 56 converts mechanical power supplied bythe HP spool 26 into electrical power and produces a power supply 66having three phase outputs. The ATU section 62 of the ATU integratedstarter-generator 56 functions to both transform the three phase outputsof the power supply 66 into a nine phase power output 68 and to step upthe voltage of the power supply.

The ATU integrated starter-generator 56 also provides a startingfunction to the aircraft. Alternatively, the ATU integrated generator 56on the HP side of the left engine system 42 may comprise a generatorthat does not provide a starting function to the aircraft. In this case,a separate starter motor connected to the accessory gearbox 60 can beprovided to perform the starting function for the aircraft. Furthermore,the left engine system 42 can include multiple generators drawingmechanical power from the HP spool 26 to produce power in order toprovide a measure of redundancy.

The ATU integrated generator 58 includes a power generation section 70and an ATU section 72. The LP spool 28 can be operably coupled with theATU integrated generator 58 by an LP drive assembly having an inputmechanically coupled to the LP spool 28 and an output mechanicallycoupled to the power generation section 70. One embodiment of the LPdrive assembly is a constant speed drive (CSD) 74 which converts thevariable speed input from the LP spool 28 to constant speed. As shownherein, the CSD 74 can be mechanically coupled to the ATU integratedgenerator 58 and drives the power generation section 70 at a constantspeed. The power generation section 70 of the ATU integrated generator58 converts mechanical power supplied by the LP spool 28 into electricalpower and produces a power supply 76 having three phase outputs. The ATUsection 72 of the ATU integrated generator 58 functions to bothtransform the three phase outputs of the power supply 76 into a ninephase power output 78 and to step up the voltage of the power supply.Due to the CSD, the power supplies 66, 76 will have constant frequency.Alternatively, the CSD 74 can be eliminated to produce a VF poweroutput.

Although the embodiment shown herein is described as using one ATUintegrated generator 58 on the LP side of the left engine system 42,another embodiment of the invention may use multiple ATU integratedgenerators 58 drawing mechanical power from the LP spool 28 to produceAC power in order to provide a measure of redundancy. Furthermore, whilea separate ATU integrated generator 58 and CSD 74 are discussed herein,an integrated drive generator which combines the CSD 74 and ATUintegrated generator 58 into a common unit can alternatively be used.

The power output 68 from the an integrated ATU integratedstarter-generator 56 is supplied to first AC/DC converter for convertingthe AC power output 68 to a DC power output 80. As illustrated, thefirst AC/DC converter can include a first rectifier device 82 and afirst filter 84 for converting the AC voltage to DC voltage and forevening out the current flow before being supplied to a first electricalbus 86. Similarly, the power output 78 from the ATU integrated generator58 is supplied to second AC/DC converter for converting the AC poweroutput 78 to a DC power output 88. As illustrated, the second AC/DCconverter can include a second rectifier device 90 and a second filter92 for converting the AC voltage to DC voltage and for evening out thecurrent flow before being supplied to a second electrical bus 94.

A motor-starter controller 96 can selectively provide power from thefirst electrical bus 86 to the ATU integrated starter-generator 56 toinitiate a starting procedure for the aircraft. The motor-startercontroller 96 can be integrated with the ATU integratedstarter-generator 56 for engine starting by connecting the motor-startercontroller 96 to the specific location of the ATU integratedstarter-generator 56 as shown FIG. 2. The three phase motor-startercontroller 96 is connected to the three phase power supply 66 to drivethe ATU integrated starter-generator 56 as a three phase starter forengine starting.

The first and second electrical buses 86, 94 are configured to supply DCpower to one or more loads (not shown) that require a DC power supply.The first and second electrical buses 86, 94 can be selectivelyconnected to enable loads to be shared by the HP spool 26 and the LPspool 28.

In operation, with the gas turbine engine 10 stared, HPT 22 rotates theHP spool 26 and the LPT 24 rotates the LP spool. The accessory gearbox64 is driven by the rotating HP spool 26, and transmits mechanical powerfrom the HP spool 26 to the ATU integrated starter-generator 56. The ATUintegrated starter-generator 56 converts mechanical power supplied bythe HP spool 26 into electrical power and produces the DC power output80. The CSD 74 is driven by the rotating LP spool 28, and transmitsmechanical power from the LP spool 28 to the ATU integrated generator58. The ATU integrated generator 58 converts the mechanical powersupplied by the LP spool 28 into electrical power and produces the DCpower output 88. The power outputs 80, 88 can be respectively providedto the electrical buses 86, 94 configured to supply DC power to one ormore loads (not shown) that require a DC power supply. Depending on thetype of load drawing power, the DC power extracted by the systemarchitecture 40 may undergo further processing before being used by theloads. The DC power outputs 50, 52 of the APU 44 and the EPS 48 can alsobe provided to the electrical buses 86, 94.

The left and right engine systems 42, 44, APU 46 and EPS 48 can provideDC power to various loads of the aircraft as needed. The various DCoutputs of the left engine system 42, the right engine system 44, theAPU 46, and the EPS 48 are integrated with appropriate switches toprovide no break power transfer (NBPT) to the aircraft.

FIG. 3 is an electrical diagram of the ATU integrated starter-generator56 and the first AC-to-DC power converter for use in the electricalpower system architecture 40 of FIG. 2. The first and second ATUintegrated generators 56, 58 and AC-to-DC power converters may besubstantially identical for both the HP spool 26 and the LP spool 28;therefore, only the HP side of the left engine system 42 will bedescribed in detail in FIG. 3 for the sake of brevity.

The ATU integrated starter-generator 56 can have a stator with threemain or primary windings 98 a to 98 c and nine secondary windings 100 ato 100 i. The main windings 98 a to 98 c each have a neutral endconnected to a common neutral point 102 and a tap 104 a to 104 cconnected to one phase output 106 a to 106 c of the three phase outputpower supply 66. The phase outputs 106 a to 106 c are provided viaconductors or lead wires to the three-phase motor-starter controller 96(FIG. 2). The secondary windings 100 a to 100 i are connected inassociated trios to one of the taps 104 a to 104 c on the main windings98 a to 98 c, and are configured to generate the nine phase power output68. In the illustrated embodiment, the primary windings 98 a to 98 c arearranged in a Wye configuration, with the overall configuration ofintegrated ATU being a star connected configuration. Alternatively, theprimary windings 98 a to 98 c can be arranged in a Delta configuration,with the overall configuration of integrated ATU being a Delta orExtended Delta connected configuration.

The nine phase power output 68 is delivered by conductors 108 a to 108 ito the rectifier device 82. The conductors 108 a to 108 i can be leadwires. The rectifier device 82 can be integrated and packaged with thegenerator 56, or provided separately from the generator 56. Therectifier device 82 can include three rectifier bridges containingmultiple diodes. The number of diodes is equal to the desired pulsecount of the ATU integrated starter-generator 56. As shown herein, thereare eighteen diodes, and so the pulse count is eighteen. Other numbersof diodes, such as 12, 18, 24, other multiples of six, etc. can also beused. One suitable type of diode is made from silicon carbide (SiC) dueto its high temperature capability. Rectifying devices other than diodescan be used.

Although the illustrated integrated starter-generator 56 is shown ashaving a pulse count of eighteen, as mentioned above, thestarter-generator 56 can be configured to have other pulse counts. Forexample, by providing two secondary windings 100 instead of three, agenerator with a pulse count of twelve can be provided. In anotherexample, by providing four secondary windings 100 instead of three, agenerator with a pulse count of twenty-four can be provided.

As illustrated, the conductors 108 a, 108 e, and 108 i are connected toa first rectifier bridge 110 having six diodes 112, the conductors 108c, 108 d, and 108 h are connected to a second rectifier bridge 114having six diodes 116, and the conductors 108 b, 108 f, and 108 g areconnected to a third rectifier bridge 118 having six diodes 120.

The three phases available on the conductors 108 a, 108 e, and 108 i arerectified by the first rectifier bridge 110, with the diodes 112delivering a first DC voltage between two first outputs 122 a and 122 b.The three phases available on the conductors 108 c, 108 d, and 108 h arerectified in parallel by the second rectifier bridge 114, with thediodes 116 delivering a second DC voltage between two second outputs 124a and 124 b. The three phases available on the conductors 108 b, 108 f,and 108 g are also rectified in parallel by the third rectifier bridge118, with the diodes 120 delivering a second DC voltage between twothird outputs 126 a and 126 b.

One output 122 a, 124 a, and 126 a from each rectifier bridge 110, 114,118 is coupled to a first interphase transformer 128 which absorbs theinstantaneous voltage differences between the outputs 122 a, 124 a, and126 a. The other output 122 b, 124 b, and 126 b from each rectifierbridge 110, 114, 118 is coupled to a second interphase transformer 130which absorbs the instantaneous voltage differences between the outputs122 b, 124 b, and 126 b. The junction points between the coils of thefirst and second interphase transformers 128, 130 form first and secondoutputs 132, 134, respectively, which are connected to the filter 84.

FIG. 4 is an electrical diagram of the stator winding for the ATUsection 62 of the ATU integrated starter-generator 56 from FIG. 3. Asdiscussed above, each main winding 98 a to 98 c extends from the commonneutral point 102 to one of the taps 104 a to 104 c. The secondarywindings 100 a to 100 c on the first main winding 98 a extend from thetap 104 a to a terminal A1, A2, A3, respectively. The secondary windings100 d to 100 f on the second main winding 98 b extend from the tap 104 bto a terminal B1, B2, B3, respectively. The secondary windings 100 g to100 i on the third main winding 98 c extend from the tap 104 c to aterminal C1, C2, C3, respectively.

FIG. 5 is a winding vector diagram for the stator winding for the ATUsection 62 of the ATU integrated starter-generator 56 of FIG. 4. Thewinding vector diagram can be used to design the stator winding for theATU section 62 of the ATU integrated starter-generator 56. The statorwinding is illustrated herein as having a pulse count of eighteen,although the stator winding can also be configured to have a pulse countin other multiple of six, such as 12, 18, 24, etc.

As can be seen, the vector diagram includes nine main vectors A1, A2,A3, B1, B2, B3, C1, C2, C3 emanating from a common point of origin O,which corresponds to the neutral point 102 of the stator winding in FIG.4. The main vectors A1-C3 represent the phase outputs which aredelivered by conductors 108 a to 108 i to the rectifier device 82 inFIG. 3. The magnitude or length V of the main vectors A1-C3 representsthe generated AC voltage and the direction or orientation of each mainvector A1-C3 represents the phase from 0-360° of the generated ACvoltage. As shown herein, the main vectors A1-C3 can have the samelength V, but differ in phase by an angle α. The main vectors A1-C3 canbe grouped, such that main vectors A1, B1, C1 represent the onethree-phase output, the main vectors A2, B2, C2 represent anotherthree-phase output, and the main vectors A3, B3, C3 represent the otherthree-phase output Each of the main vectors A1, B1, and C1 includes twosub-vectors X1, X2, Y1, Y2, Z1, Z2 emanating from a point P (whichcorresponds to the taps 104 a-c in FIG. 4) to meet one of the other mainvectors A2, A3, B2, B3, C2, C3. The distance between the common point oforigin O and point P is represented as length L1. The distance frompoint P to the end of main vector A1 is represented as length L2. Assuch, the length V of the main vector A1, and therefore all the othermain vectors A2, A3, B2, B3, C2, C3 is given by the followingrelationship:

V=|L1|+|L2|

Sub-vector X2 extends from main vector A1 to main vector A3 at an angleθ1 and has a length L3. While not shown in FIG. 5, the other sub-vectorsX2, Y1, Y2, Z1, Z2 also have a length L3, and extend from the associatedmain vector at an angle equal to θ1. The ends of main vectors A1 and A3are separated by a distance d, which together with lengths L2 and L3,form a triangle having vertices defining interior angles θ1, θ2, and θ3.The lengths L1-L3 and angles θ1 and a can be selected to design thestator winding for the ATU section 62 of the ATU integratedstarter-generator 56 from FIG. 3.

The angles α, θ1, θ2, and θ3 are dependent on the number of pulses N,and the relationship therebetween is given by the following equations:

α = 360/N${\theta \; 3} = {\left( {{180{^\circ}} - \frac{360}{N}} \right) \div 2}$θ 2 = 180^(∘) − θ 1 − θ 3

In this example, it can be given that N=18 and θ1=60°. Thus, angleα=20°, angle θ3=80° and angle θ2=40°. It is understood that θ2 or θ3could be given instead of θ1.

The relationship between the lengths L2, L3, d and the angles θ1, θ2,and θ3 is known from the law of sines as:

$\frac{d}{\sin \; \theta \; 1} = {\frac{{L\; 2}}{\sin \; \theta \; 2} = \frac{{L\; 3}}{\sin \; {\theta 3}}}$

The distance d from the end of main vector A1 to the end of main vectorA3 is given by the following relationship:

${d} = {2\mspace{14mu} V\mspace{14mu} \sin \frac{180}{N}}$

Using the law of sines, the lengths L2 and L3 are therefore given by thefollowing relationships:

${{L\; 2}} = {\frac{{d}\sin \; {\theta 2}}{\sin \; \theta \; 1} = \frac{2\mspace{14mu} V\mspace{14mu} \sin \frac{180}{N}\sin \; \theta \; 2}{\sin \; \theta \; 1}}$${{L\; 3}} = {\frac{{d}\sin \; \theta \; 3}{\sin \; \theta \; 1} = \frac{2\mspace{14mu} V{\mspace{11mu} \;}\sin \frac{180}{N}\sin \; \theta \; 3}{\sin \; \theta \; 1}}$

Using the relationship between the voltage V and lengths L1, L2, thelength L1 can be determined using the following relationship:

|L1|=(V−|L2|)

Thus, by knowing the desired number of pulses N, the desired voltage V,and at least one other variable, the main stator winding for the ATUsection 62 of the ATU integrated starter-generator 56 from FIG. 3 can bedesigned. In this case, the other variable given is θ1. However, it willbe understood that another variable, such as a different angle or alength, could be given instead.

FIG. 6 is a schematic block diagram of an electrical power systemarchitecture 140 according to a second embodiment of the invention. Thesystem architecture 140 may be substantially similar to the systemarchitecture 40 shown in FIG. 2; therefore, like elements will bereferred to using the same reference numerals. One difference betweenthe system architecture 140 shown in FIG. 6 and the system architecture40 shown in FIG. 2 is that, for both ATU integrated generators 56, 58,the ATU section 62, 72 functions to transform the three phase outputs ofthe power supply 66, 76 into a nine phase power output 142, 144 byadding two secondary windings instead of adding three windings.

FIG. 7 is an electrical diagram of the ATU integrated starter-generator56 and the first AC-to-DC power converter for use in the electricalpower system architecture 140 of FIG. 6. The first and second ATUintegrated generators 56, 58 and AC-to-DC power converters may besubstantially identical for both the HP spool 26 and the LP spool 28;therefore, only the HP side of the left engine system 42 will bedescribed in detail in FIG. 7 for the sake of brevity.

The ATU integrated starter-generator 56 can have six secondary windings146 a to 146 f connected in associated duos to one of the taps 104 a to104 c on the main windings 98 a to 98 c. In the illustrated embodiment,the primary windings 98 a to 98 c are arranged in a Wye configuration,with the overall configuration of integrated ATU being a fork connectedconfiguration. Alternatively, the primary windings 98 a to 98 c can bearranged in a Delta configuration.

The nine phase power output 142 is delivered by conductors 148 a to 148i and 150 a to 150 c to the rectifier device 82. The conductors 148 a,148 c, and 148 e are connected to the second rectifier bridge 114 andthe conductors 148 b, 148 d, 148 f are connected to the third rectifierbridge 118. Conductors 150 a to 150 c extend from primary windings 98 ato 98 c, and are connected to the first rectifier bridge 110. Theconductors 148 a to 148 i and 150 a to 150 c can be lead wires. Theremaining rectification and filtering of the power is the same asdescribed above for FIG. 3.

Although the illustrated integrated starter-generator 56 is shown ashaving a pulse count of eighteen, the starter-generator 56 can beconfigured to have other pulse counts. For example, by providing onesecondary winding 146 instead of two, a generator with a pulse count oftwelve can be provided. In another example, by providing three secondarywindings 146 instead of two, a generator with a pulse count oftwenty-four can be provided.

FIG. 8 is an electrical diagram of the stator winding for the ATUsection 62 of the ATU integrated starter-generator 56 from FIG. 7. Asdiscussed above, each main winding 98 a to 98 c extends from the commonneutral point 102 to one of the taps 104 a to 104 c. The secondarywindings 146 a and 146 b on the first main winding 98 a extend from thetap 104 a, also shown as terminal A1, to a terminal A2 and A3,respectively. The secondary windings 146 c and 146 d on the second mainwinding 98 b extend from the tap 104 b, as shown as terminal B1, to aterminal B2 and B3, respectively. The secondary windings 146 e and 146 fon the third main winding 98 c extend from the tap 104 c, also shown asterminal C1, to a terminal C2 and C3, respectively.

FIG. 9 is a winding vector diagram for the stator winding for the ATUsection 62 of the ATU integrated starter-generator 56 of FIG. 8. Thewinding vector diagram can be used to design the stator winding for theATU section 62 of the ATU integrated starter-generator 56. The statorwinding is illustrated herein as having a pulse count of eighteen,although the stator winding can also be configured to have a pulse countin other multiple of six, such as 12, 18, 24, etc.

As can be seen, the vector diagram includes nine main vectors A1, A2,A3, B1, B2, B3, C1, C2, C3 emanating from a common point of origin O,which corresponds to the neutral point 102 of the stator winding in FIG.8. The main vectors A1-C3 represent the phase outputs which aredelivered by conductors 148 a-f and 150 a-c to the rectifier device 82in FIG. 7. The magnitude or length V of the main vectors A1-C3represents the generated AC voltage and the direction or orientation ofeach main vector A1-C3 represents the phase from 0-360° of the generatedAC voltage. As shown herein, the main vectors A1-C3 can have the samelength V, but differ in phase by an angle α.

Each of the main vectors A1, B1, and C1 includes two sub-vectors X1, X2,Y1, Y2, Z1, Z2 emanating from an end point E (which corresponds to thetaps 104 a-c in FIG. 8) to meet one of the other main vectors A2, A3,B2, B3, C2, C3. The distance between the common point of origin O andend point E is represented as length L1. As such, the length V of themain vector A1, and, therefore, all the other main vectors A2, A3, B2,B3, C2, C3 is given by the following relationship:

V=|L1|

Sub-vector X2 extends from main vector A1 to main vector A3 at an angleθ and has a length L2. While not shown in FIG. 9, the other sub-vectorsX2, Y1, Y2, Z1, Z2 also have a length L2, and extend from the associatedmain vector at an angle equal to θ. The lengths L1 and L2 and angles θand α can be selected to design the stator winding for the ATU section62 of the ATU integrated starter-generator 56 from FIG. 7.

The angles θ and α are dependent on the number of pulses N, and therelationship therebetween is given by the following equations:

$\theta = {\left( {{180{^\circ}} - \frac{360}{N}} \right) \div 2}$α = 360/N

In this example, it can be given that N=18. Thus, angle α=20° and angleθ=80°.

The length L2 from end point E to the end of main vector A3 is given bythe following relationship:

${{L\; 2}} = {2\mspace{14mu} V\mspace{14mu} \sin \; \frac{180}{N}}$

Thus, by knowing the desired number of pulses N and the desired voltageV, the main stator winding for the ATU section 62 of the ATU integratedstarter-generator 56 from FIG. 3 can be designed.

FIG. 10 is a schematic block diagram of an electrical power systemarchitecture 160 according to a third embodiment of the invention. Thesystem architecture 160 may be substantially similar to the systemarchitecture 40 shown in FIG. 2; therefore, like elements will bereferred to using the same reference numerals. One difference betweenthe system architecture 160 shown in FIG. 10 and the system architecture40 shown in FIG. 2 is that the ATU section 62 includes an AC poweroutput 162 that is supplied to an AC bus 164, in addition to the ninephase power output 68.

FIG. 11 is an electrical diagram of the ATU integrated starter-generator56 and the first AC-to-DC power converter for use in the electricalpower system architecture 160 of FIG. 10. The ATU integratedstarter-generator 56 can be substantially similar to the ATU integratedstarter-generator 56 of the first embodiment shown in FIG. 3, with theexception that additional secondary windings 166 a to 166 c are providedon the main windings 98 a to 98 c. The additional secondary windings 166a to 166 c can be connected by one of the taps 104 a to 104 c connectedto one phase output 106 a to 106 c of the three phase output powersupply 66. The phase outputs 106 a to 106 c are provided to thethree-phase motor-starter controller 96 (FIG. 10). The AC power output162 is delivered by conductors 168 a to 168 c from the windings 166 a to166 c to the AC bus 164 (FIG. 10) without being converted to DC by therectifier device 82. The conductors 168 a to 168 c can be lead wires.The remaining rectification and filtering of the DC power is the same asdescribed above for FIG. 3.

The system architecture disclosed herein provides an integrated ATUgenerator for an aircraft. One advantage that may be realized in thepractice of some embodiments of the described systems and methods isthat the traditional high pulse count ATU can be eliminated, and itsequivalence is integrated into at least one of the generator (s) that isconnected to a rectifying device to generate a low harmonic content DCoutput. This arrangement significantly reduces the weight of the engine,and can simplify the cooling for engine components. The provision of theintegrated ATU generator can also eliminate the space needed for aseparate ATU in the aircraft.

Another advantage that may be realized in the practice of someembodiments of the described systems and methods is that the ATUintegrated starter-generator 56 does not jeopardize the use of the threephase motor-starter controller 96, since the motor-starter controller 96is connected to the three phase power supply 66 before it is transformedto a nine phase power output in the ATU section 62 of the ATU integratedstarter-generator 56.

Another advantage that may be realized in the practice of someembodiments of the described systems and methods is that DC power can beextracted from both spools 26, 28 of a gas turbine engine 10. Theoperating efficiency of the gas turbine engine 10 is also increased byseamlessly controlling the power drawn from HP and LP spools 26, 28. Inaddition to the DC power drawn from the HP and LP spools 26, 28, the DCoutputs 50, 52 from the APU 46 and the EPS 48 can be integrated toprovide no break power transfer (NBPT).

Another advantage that may be realized in the practice of someembodiments of the described systems and methods is that the systemarchitecture(s) can offer a level of redundant DC power generation,since DC power can be extracted from the LP spool 28 as well as the HPspool 26 of the gas turbine engine 10. Drawing power from both spools26, 28 offers increased redundancy for DC power, such that in the eventof a failure of one of the spools 26, 28 or generators 42, 44, DC powermay still be extracted from the remaining operational spool 26, 28 andgenerator 42, 44.

Still another advantage that may be realized in the practice of someembodiments of the described systems and methods is the avoidance ofengine stall issues that are typically encountered during a descend modeof the aircraft by sharing the DC load between the HP and LP spools 26,28. Being able to draw power from the LP spool as well as the HP spoolpermits allows the aircraft to run at lower rpms during descent withoutrisk of stall, thereby preserving fuel efficiency of the aircraft.

Yet another advantage that may be realized in the practice of someembodiments of the described systems and methods is that both AC and DCpower can be extracted from the gas turbine engine 10. The thirdembodiment of the invention described herein in particular provides asystem architecture which gives an air framer access to both types ofpower, such that an air framer can select either type of power for aparticular application on an aircraft.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A generator comprising: a stator having threemain windings; at least two secondary windings connected to each of thethree main windings to form an integrated auto transformer unit; a firstset of conductors connected to the three main windings; and a second setof conductors connected to each of the at least two secondary windings.2. The generator of claim 1 wherein the at least two secondary windingscomprise three secondary windings.
 3. The generator of claim 2 whereinthe three secondary windings are connected to each other in a deltaconfiguration.
 4. The generator of claim 1 wherein the three mainwindings are connected to each other in a Wye configuration.
 5. Thegenerator of claim 1 wherein the three main windings are connected toeach other in a delta configuration.
 6. The generator of claim 1 whereinthe integrated auto transformer unit is configured to transmit pulses ina multiple of six.
 7. The generator of claim 1 wherein the integratedauto transformer unit comprises a pulse count of one of 12, 18, and 24.8. The generator of claim 1, further comprising a third set of conductsconnected to each of the first set of conductors.
 9. The generator ofclaim 1, further comprising one additional winding connected to each ofthe three main windings and configured to deliver AC power to a bus. 10.A gas turbine engine comprising the generator of claim
 1. 11. The gasturbine engine of claim 10 wherein the generator further comprises arotor operably coupled with a spool of the gas turbine engine.